This invention relates generally to expansion or anchor bolt assemblies adapted to secure articles to masonry surfaces, and more particularly to an assembly which when installed in a hole drilled in the masonry is rendered vibration-proof so that the bolt cannot be loosened even under severe vibratory conditions.
It is frequently necessary to bolt fixtures and other heavy parts to the surface of brickwork, concrete and other forms of masonry. For this purpose, it is the conventional practice to make use of an anchor bolt assembly having an expansible shell which serves to securely retain the bolt within the masonry hole. Anchor bolt assemblies come in diverse forms, but in all such assemblies, some means are provided to bring about the dilation of an expansible shell or similar component against the wall of the masonry hole to anchor the bolt therein.
Thus in the prior Giannuzzi U.S. Pat. No. 3,766,819, the bolt whose threaded front end protrudes out of the masonry hole has a waist of reduced diameter adjacent its rear end, the waist being encircled by an expansible shell. The rear end of the bolt has a conical formation such that when during a fastening operation the bolt is slowly withdrawn from the hole by a nut turning on its threaded front end, the rear end cone of the bolt is axially advanced towards and into the shell to expand the shell against the wall of the hole, thereby anchoring the bolt in the masonry.
A similar expansion-type fastener is disclosed in the McIntyre U.S. Pat. No. 4,056,037. One serious objection to anchor bolt assemblies of these known types is that, once installed, the bolt is permanently anchored in the masonry and cannot be removed therefrom, so that it always protrudes from the masonry, even when no longer in use.
Another type of expansion anchor is that disclosed in the Zifferer U.S. Pat. No. 3,742,809 in which the bolt has a conically-tapered and threaded rear end portion which cooperates with an internally-tapered and threaded expansion sleeve, such that when the bolt is turned with a wrench or other torque-producing tool, the bolt is caused to rotate into the expansion sleeve which is thereby forced outwardly to anchor the bolt in the hole drilled in masonry. While this type of anchor bolt makes it possible to later remove the bolt, leaving the sleeve within the hole, it is a difficult anchor to install properly. The head of the bolt must be located away from the face of the fixture before tightening. The installer must guess at the amount of expansion that will be required to secure the proper hold on the masonry since the bolt must contact the fixture being fastened when the expansion is complete.
The primary concern of the present invention is with anchor bolt assemblies of the type disclosed in the Dempsey U.S. Pat. No. 2,988,950 in which a wedge nut is received on the threaded rear end of the bolt. When the bolt is turned by a wrench, this bolt is caused to travel downwardly on the bolt to enter and expand an expansible shell, forcing this shell into tight engagement with the wall of the hole in which the bolt is inserted. The main deficiency of bolt anchors of this known type is that the wedge nut is never locked to the bolt, and under severe vibratory conditions, the bolt may be loosened from the nut, thereby weakening the anchor.
The following patents represent other relevant prior art known to applicant:
Kinnear, U.S. Pat. No. 704,547 PA1 Craig, U.S. Pat. No. 332,701 PA1 Ploch, U.S. Pat. No. 3,523,482 PA1 Polos, U.S. Pat. No. 3,878,264 PA1 Polmon, U.S. Pat. No. 3,270,793 PA1 McNulty, U.S. Pat. No. 798,440 PA1 Lewis, U.S. Pat. No. 2,667,099